/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2013-2014 sagyf Yang. The Four Group.
 */

DateInput = (function($) { // Localise the $ function

    function DateInput(el, opts) {
        if (typeof(opts) != "object") opts = {};
        $.extend(this, DateInput.DEFAULT_OPTS, opts);

        this.input = $(el);
        this.bindMethodsToObj("show", "hide", "hideIfClickOutside", "keydownHandler", "selectDate");

        this.build();
        this.selectDate();
        this.hide();
    };
    DateInput.DEFAULT_OPTS = {
        month_names: ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"],
        short_month_names: ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
        short_day_names: ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
        start_of_week: 1
    };
    DateInput.prototype = {
        build: function() {
            var monthNav = $('<p class="month_nav">' +
                '<span class="button prev" title="[Page-Up]">&#171;</span>' +
                ' <span class="month_name"></span> ' +
                '<span class="button next" title="[Page-Down]">&#187;</span>' +
                '</p>');
            this.monthNameSpan = $(".month_name", monthNav);
            $(".prev", monthNav).click(this.bindToObj(function() { this.moveMonthBy(-1); }));
            $(".next", monthNav).click(this.bindToObj(function() { this.moveMonthBy(1); }));

            var yearNav = $('<p class="year_nav">' +
                '<span class="button prev" title="[Ctrl+Page-Up]">&#171;</span>' +
                ' <span class="year_name"></span> ' +
                '<span class="button next" title="[Ctrl+Page-Down]">&#187;</span>' +
                '</p>');
            this.yearNameSpan = $(".year_name", yearNav);
            $(".prev", yearNav).click(this.bindToObj(function() { this.moveMonthBy(-12); }));
            $(".next", yearNav).click(this.bindToObj(function() { this.moveMonthBy(12); }));

            var nav = $('<div class="nav"></div>').append(monthNav, yearNav);

            var tableShell = "<table><thead><tr>";
            $(this.adjustDays(this.short_day_names)).each(function() {
                tableShell += "<th>" + this + "</th>";
            });
            tableShell += "</tr></thead><tbody></tbody></table>";

            this.dateSelector = this.rootLayers = $('<div class="date_selector"></div>').append(nav, tableShell).insertAfter(this.input);

            if ($.browser.msie && $.browser.version < 7) {
                // The ieframe is a hack which works around an IE <= 6 bug where absolutely positioned elements
                // appear behind select boxes. Putting an iframe over the top of the select box prevents this.
                this.ieframe = $('<iframe class="date_selector_ieframe" frameborder="0" src="#"></iframe>').insertBefore(this.dateSelector);
                this.rootLayers = this.rootLayers.add(this.ieframe);

                // IE 6 only does :hover on A elements
                $(".button", nav).mouseover(function() { $(this).addClass("hover") });
                $(".button", nav).mouseout(function() { $(this).removeClass("hover") });
            };

            this.tbody = $("tbody", this.dateSelector);

            this.input.change(this.bindToObj(function() { this.selectDate(); }));
            this.selectDate();
        },

        selectMonth: function(date) {
            var newMonth = new Date(date.getFullYear(), date.getMonth(), 1);

            if (!this.currentMonth || !(this.currentMonth.getFullYear() == newMonth.getFullYear() &&
                this.currentMonth.getMonth() == newMonth.getMonth())) {
                // We have moved to a different month and so need to re-draw the table
                this.currentMonth = newMonth;

                // Work out the range of days we will draw
                var rangeStart = this.rangeStart(date), rangeEnd = this.rangeEnd(date);
                var numDays = this.daysBetween(rangeStart, rangeEnd);
                var dayCells = "";

                // Draw each of the days
                for (var i = 0; i <= numDays; i++) {
                    var currentDay = new Date(rangeStart.getFullYear(), rangeStart.getMonth(), rangeStart.getDate() + i, 12, 00);

                    if (this.isFirstDayOfWeek(currentDay)) dayCells += "<tr>";

                    if (currentDay.getMonth() == date.getMonth()) {
                        dayCells += '<td class="selectable_day" date="' + this.dateToString(currentDay) + '">' + currentDay.getDate() + '</td>';
                    } else {
                        dayCells += '<td class="unselected_month" date="' + this.dateToString(currentDay) + '">' + currentDay.getDate() + '</td>';
                    };

                    if (this.isLastDayOfWeek(currentDay)) dayCells += "</tr>";
                };
                this.tbody.empty().append(dayCells);

                // Write the month and year in the header
                this.monthNameSpan.empty().append(this.monthName(date));
                this.yearNameSpan.empty().append(this.currentMonth.getFullYear());

                $(".selectable_day", this.tbody).click(this.bindToObj(function(event) {
                    this.changeInput($(event.target).attr("date"));
                }));

                $("td[date=" + this.dateToString(new Date()) + "]", this.tbody).addClass("today");

                $("td.selectable_day", this.tbody).mouseover(function() { $(this).addClass("hover") });
                $("td.selectable_day", this.tbody).mouseout(function() { $(this).removeClass("hover") });
            };

            $('.selected', this.tbody).removeClass("selected");
            $('td[date=' + this.selectedDateString + ']', this.tbody).addClass("selected");
        },

        // Select a particular date. If the date is not specified it is read from the input. If no date is
        // found then the current date is selected. The selectMonth() function is responsible for actually
        // selecting a particular date.
        selectDate: function(date) {
            if (typeof(date) == "undefined") {
                date = this.stringToDate(this.input.val());
            };
            if (!date) date = new Date();

            this.selectedDate = date;
            this.selectedDateString = this.dateToString(this.selectedDate);
            this.selectMonth(this.selectedDate);
        },

        // Write a date string to the input and hide. Trigger the change event so we know to update the
        // selectedDate.
        changeInput: function(dateString) {
            this.input.val(dateString).change();
            this.hide();
        },

        show: function() {
            this.rootLayers.css("display", "block");
            $([window, document.body]).click(this.hideIfClickOutside);
            this.input.unbind("focus", this.show);
            $(document.body).keydown(this.keydownHandler);
            this.setPosition();
        },

        hide: function() {
            this.rootLayers.css("display", "none");
            $([window, document.body]).unbind("click", this.hideIfClickOutside);
            this.input.focus(this.show);
            $(document.body).unbind("keydown", this.keydownHandler);
        },

        // We should hide the date selector if a click event happens outside of it
        hideIfClickOutside: function(event) {
            if (event.target != this.input[0] && !this.insideSelector(event)) {
                this.hide();
            };
        },

        // Returns true if the given event occurred inside the date selector
        insideSelector: function(event) {
            var offset = this.dateSelector.position();
            offset.right = offset.left + this.dateSelector.outerWidth();
            offset.bottom = offset.top + this.dateSelector.outerHeight();

            return event.pageY < offset.bottom &&
                event.pageY > offset.top &&
                event.pageX < offset.right &&
                event.pageX > offset.left;
        },

        // Respond to various different keyboard events
        keydownHandler: function(event) {
            switch (event.keyCode)
            {
                case 9: // tab
                case 27: // esc
                    this.hide();
                    return;
                    break;
                case 13: // enter
                    this.changeInput(this.selectedDateString);
                    break;
                case 33: // page up
                    this.moveDateMonthBy(event.ctrlKey ? -12 : -1);
                    break;
                case 34: // page down
                    this.moveDateMonthBy(event.ctrlKey ? 12 : 1);
                    break;
                case 38: // up
                    this.moveDateBy(-7);
                    break;
                case 40: // down
                    this.moveDateBy(7);
                    break;
                case 37: // left
                    this.moveDateBy(-1);
                    break;
                case 39: // right
                    this.moveDateBy(1);
                    break;
                default:
                    return;
            }
            event.preventDefault();
        },

        stringToDate: function(string) {
            var matches;
            if (matches = string.match(/^(\d{1,2}) ([^\s]+) (\d{4,4})$/)) {
                return new Date(matches[3], this.shortMonthNum(matches[2]), matches[1], 12, 00);
            } else {
                return null;
            };
        },

        dateToString: function(date) {
            return date.getDate() + " " + this.short_month_names[date.getMonth()] + " " + date.getFullYear();
        },

        setPosition: function() {
            var offset = this.input.offset();
            this.rootLayers.css({
                top: offset.top + this.input.outerHeight(),
                left: offset.left
            });

            if (this.ieframe) {
                this.ieframe.css({
                    width: this.dateSelector.outerWidth(),
                    height: this.dateSelector.outerHeight()
                });
            };
        },

        // Move the currently selected date by a particular number of days
        moveDateBy: function(amount) {
            var newDate = new Date(this.selectedDate.getFullYear(), this.selectedDate.getMonth(), this.selectedDate.getDate() + amount);
            this.selectDate(newDate);
        },

        // Move the month of the currently selected date by a particular number of months. If we are moving
        // to a month which does not have enough days to represent the current day-of-month, then we
        // default to the last day of the month.
        moveDateMonthBy: function(amount) {
            var newDate = new Date(this.selectedDate.getFullYear(), this.selectedDate.getMonth() + amount, this.selectedDate.getDate());
            if (newDate.getMonth() == this.selectedDate.getMonth() + amount + 1) {
                // We have moved too far. For instance 31st March + 1 month = 1st May, not 30th April
                newDate.setDate(0);
            };
            this.selectDate(newDate);
        },

        // Move the currently displayed month by a certain amount. This does *not* move the currently
        // selected date, so we end up viewing a month with no visibly selected date.
        moveMonthBy: function(amount) {
            var newMonth = new Date(this.currentMonth.getFullYear(), this.currentMonth.getMonth() + amount, this.currentMonth.getDate());
            this.selectMonth(newMonth);
        },

        monthName: function(date) {
            return this.month_names[date.getMonth()];
        },

        // A hack to make "this" refer to this object instance when inside the given function
        bindToObj: function(fn) {
            var self = this;
            return function() { return fn.apply(self, arguments) };
        },

        // See above
        bindMethodsToObj: function() {
            for (var i = 0; i < arguments.length; i++) {
                this[arguments[i]] = this.bindToObj(this[arguments[i]]);
            };
        },

        // Finds out the array index of a particular value in that array
        indexFor: function(array, value) {
            for (var i = 0; i < array.length; i++) {
                if (value == array[i]) return i;
            };
        },

        // Finds the number of a given month name
        monthNum: function(month_name) {
            return this.indexFor(this.month_names, month_name);
        },

        // Finds the number of a given short month name
        shortMonthNum: function(month_name) {
            return this.indexFor(this.short_month_names, month_name);
        },

        // Finds the number of a given day name
        shortDayNum: function(day_name) {
            return this.indexFor(this.short_day_names, day_name);
        },

        // Works out the number of days between two dates
        daysBetween: function(start, end) {
            start = Date.UTC(start.getFullYear(), start.getMonth(), start.getDate());
            end = Date.UTC(end.getFullYear(), end.getMonth(), end.getDate());
            return (end - start) / 86400000;
        },

        /*
         changeDayTo: Given a date, move along the date line in the given direction until we reach the
         desired day of week.

         The maths is a bit complex, here's an explanation.

         Think of a continuous repeating number line like:

         .. 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 ..

         We are essentially trying to find the difference between two numbers
         on the line in one direction (dictated by the sign of direction variable).
         Unfortunately Javascript's modulo operator works such that -5 % 7 = -5,
         instead of -5 % 7 = 2, so we need to only work with the positives.

         To find the difference between 1 and 4, going backwards, we can treat 1
         as (1 + 7) = 8, so the different is |8 - 4| = 4. If we don't cross the
         boundary between 0 and 6, for instance to find the backwards difference
         between 5 and 2, |(5 + 7) - 2| = |12 - 2| = 10. And 10 % 7 = 3.

         Going forwards, to find the difference between 4 and 1, we again treat 1
         as (1 + 7) = 8, and the difference is |4 - 8| = 4. If we don't cross the
         boundary, the difference between 2 and 5 is |2 - (5 + 7)| = |2 - 12| = 10.
         And 10 % 7 = 3.

         Once we have the positive difference in either direction represented as a
         absolute value, we can multiply it by the direction variable to get the difference
         in the desired direction.

         We can condense the two methods into a single equation:

         backwardsDifference = direction * (|(currentDayNum + 7) - dayOfWeek| % 7)
         = direction * (|currentDayNum - dayOfWeek + 7|  % 7)

         forwardsDifference = direction * (|currentDayNum - (dayOfWeek + 7)| % 7)
         = direction * (|currentDayNum - dayOfWeek - 7| % 7)

         (The two equations now differ only by the +/- 7)

         difference = direction * (|currentDayNum - dayOfWeek - (direction * 7)| % 7)
         */
        changeDayTo: function(dayOfWeek, date, direction) {
            var difference = direction * (Math.abs(date.getDay() - dayOfWeek - (direction * 7)) % 7);
            return new Date(date.getFullYear(), date.getMonth(), date.getDate() + difference);
        },

        // Given a date, return the day at the start of the week *before* this month
        rangeStart: function(date) {
            return this.changeDayTo(this.start_of_week, new Date(date.getFullYear(), date.getMonth()), -1);
        },

        // Given a date, return the day at the end of the week *after* this month
        rangeEnd: function(date) {
            return this.changeDayTo((this.start_of_week - 1) % 7, new Date(date.getFullYear(), date.getMonth() + 1, 0), 1);
        },

        // Is the given date the first day of the week?
        isFirstDayOfWeek: function(date) {
            return date.getDay() == this.start_of_week;
        },

        // Is the given date the last day of the week?
        isLastDayOfWeek: function(date) {
            return date.getDay() == (this.start_of_week - 1) % 7;
        },

        // Adjust a given array of day names to begin with the configured start-of-week
        adjustDays: function(days) {
            var newDays = [];
            for (var i = 0; i < days.length; i++) {
                newDays[i] = days[(i + this.start_of_week) % 7];
            };
            return newDays;
        }
    };

    $.fn.date_input = function(opts) {
        return this.each(function() { new DateInput(this, opts); });
    };
    $.date_input = { initialize: function(opts) {
        $("input.date_input").date_input(opts);
    } };

    return DateInput;
})(jQuery); // End localisation of the $ function